HARDWICK — While sets of whipsawed wires responded with a loud, echoic twang as work continued on one part of the Susquehanna-Roseland transmission project, crews went ahead with a second part of the project that aims to protect manmade and natural flying objects.

Since the nearly 200-foot-tall towers went up during winter, the one atop Kittatinny Ridge announced its presence far and wide with a bright blinking beacon, visible from miles away and creating calls to police and newsrooms about the strange new sight on the horizon.

As part of the $1.5 billion project, and necessary to get approval from the National Park Service for the new lines to cross the Delaware Water Gap National Recreation Area and two other units of the park service, Public Service Electric & Gas and PPL, the utilities building the line, agreed to several safety measures.

One is to alert low-flying airplanes of the presence of the new wires, more than twice as high as the ones they replaced, both at the top of the ridge and along the Delaware River on the west side of the ridge and Sand Pond on the east side.

The other project, which was a vital concern to ecologists, was to keep birds, especially large raptors like eagles and hawks, from flying into the lines.

That part of the project involves a couple of steps, making the wires appear larger than they are and documenting what effect the wires have on the birds and, if possible, how many times the birds collide with the wires.

Jason Kalwa, manager of the project for PSE&G, said the bird avoidance system consists of spirals attached to the

topmost set of two wires. Known as shield wires, they carry information about the condition of the two sets transmission lines below, with each set capable of carrying a half-million volts (500 kilovolts) of electricity.

The Kittatinny Ridge, as it is known in New Jersey, is a major north-south flyway for migrating birds, especially raptors, which use the uplifting currents of the ridge to soar from Connecticut to near Maryland.

The topmost shield wires, for the four sections that cross over the top of the ridge through the park, are outfitted with spirals, several times larger than the shield wires, and give birds the optical clue that this is something to avoid.

Similar spirals are being installed along the wires where they cross the river since that route is also a migratory route for smaller songbirds.

In both places, the company is also installing a series of infrared cameras and detectors that will trigger the cameras when birds are detected flying close to the wires.

Even though there are thousands of volts of electricity in the lines, the detector/camera system doesn’t draw its power from the lines. Several of the transmission towers have been outfitted with large solar panels, which will feed the batteries that run the camera/detector system.

Kalwa said the system isn’t just for the migrating period, but pretty much year round since there are bald eagle nests all along the valley, and the Delaware River is a winter home for eagles since long stretches of the river remain ice-free.

For manmade flying objects, the beacons, one atop the ridge, one set on either side of the river and one set at Sand Pond, could be kept on 24/7 as they are now.

But as part of the volumes of environmental safeguards set down for this project, the beacons will only come on when there is a low-flying aircraft within about 3 1/2 miles horizontally, Kalwa said.

Inside each of the two globes atop towers on each side of the ridge is a radar antenna that is monitoring the sky.

Although there are usually planes flying overhead, most of them are on a higher flight path taking them to major airports such as Newark, Teterboro, Stewart, Philadelphia or Allentown and wouldn’t be flying low enough to be concerned.

But there are also local airports, such as Pocono, East Stroudsburg, Newton, Sussex, Blairstown and Andover, as well as some private airstrips that serve local traffic and sightseeing flights through the valley.

Kalwa said both projects will be done by midsummer.

Kalwa said the radar project should be done by the end of May when the beacons will be switched over to the detector system, rather than on all the time.

During construction, the Appalachian Trail, a unit of the National Park Service, has been rerouted.

The normal trail route followed the right-of-way for a ways at the top of the ridge and, with the vegetation kept low, provided amazing vistas both east and west.

The detour route makes a straight line across the right of way on the western side of the ridge with the new path outlined by orange fences. The route then snakes its way to the top of the ridge through some woods, rejoining the trail.

And the overhead twang?

Kalwa said the sound was of crews “tensioning” the new 500-kilovolt lines that have been strung between the towers but still hang from large pulleys. At each end of lengthy sections are large machines that are pulling the wires to the required tension to hang where they can expand and contract with the weather.

During the process, the three large cables that make up one set of lines are not connected to keep a proper distance apart.

As the wind and the tensioning process moves the lines, they often bang into each other. The resulting shockwave, while not damaging to the lines, does create sounds that travel along the lines.